Spectroscopic and computational approaches to unravel the mode of binding between a isoflavone, biochanin-A and calf thymus DNA.

In the present study, attempt was made to explore the interaction between biochanin-A (BioA) and calf thymus DNA (ctDNA) by employing fluorescence spectroscopy, absorption spectroscopy, circular dichroism (CD), DNA melting studies, viscosity measurements, and molecular modeling methods. A well-known fluorescence probe, acridine orange (AO) was used in the present study in order to enhance the emission intensity of weakly fluorescent ctDNA. Quenching in emission intensity of ctDNA-AO system was observed in the presence of different concentrations of BioA, suggesting that BioA has interacted with ctDNA. The hyperchromic effect observed upon the addition of BioA in the absorption spectra of ctDNA-AO without any shift in its absorption maximum revealed that BioA was bound to ctDNA through groove mode of binding. Further the groove mode of binding of BioA to ctDNA was confirmed by DNA melting studies, viscosity measurements, and molecular docking studies. The results of fluorescence measurements that were carried out at different temperature indicated that the BioA has quenched the emission intensity of ctDNA-AO through static mode of quenching mechanism. Thermodynamic parameters revealed that the BioA-ctDNA-AO system was stabilized by van der Waals forces and hydrogen bonding. The effect of binding of BioA on the conformation of ctDNA was examined by circular dichroism studies.